Old Faithful was named by the first official expedition to Yellowstone, the Washburn Expedition of 1870. They were impressed by its size and frequency. Old Faithful erupts every 35 to 120 minutes for 1 1/2 to 5 minutes. Its maximum height ranges from 90 to 184 feet.

It is not the biggest or the most regular geyser in Yellowstone but it is the biggest regular geyser. Furthermore, it has been erupting in nearly the same fashion throughout the recorded history of the park. Through the years, it has become one of the most studied geysers. One result of this close observation is that the Park Rangers are able to predict its eruptions fairly accurately. This makes Old Faithful geyser one of the easiest geysers in Yellowstone to see.

老忠诚间歇泉是黄石国家公园的最著名的间歇泉。 它每35－120分钟喷发一次，喷发高度达30－60米，喷发时间1.5-5分钟，喷水温度摄氏90度左右。黄石公园有记录历史以来，这个间歇泉就一直这样不停歇地有规律地喷发，因此得名“老忠诚”。喷泉周围的饭馆中有时间指示盘标示着下一次的喷发时间，误差在5分钟之内。